Fix for upstream change to ELFObjectFile::getELFFile
Fix for upstream change to ELFObjectFile::getELFFile

Upstream commit ffbce65f95ee "Make ELFObjectFile::getELFFile return reference."
needs a corresponding change in the ElfLinker.

googlestadia/llpc,GPUOpen-Drivers/llpc,googlestadia/llpc,googlestadia/llpc,GPUOpen-Drivers/llpc,GPUOpen-Drivers/llpc,googlestadia/llpc,googlestadia/llpc,GPUOpen-Drivers/llpc,GPUOpen-Drivers/llpc